The "standard" lenses would be 105mm for 6x7, and 150mm for 4x5". Then it all depends on your enlarger; what is the maximum enlargement possible with those lenses?
The extreme case here is the 11x linear to enlarge 6x7 to 20x24", which is just barely within the capabilities of a Durst 138S - without turning it horizontal. The same elevation gives 6.5x with a 150mm lens, which could give a 26x31" print.
Once things are turned on the side, the size is only limited by the length of your darkroom.
A shorter lens (with wide coverage) could be substituted for either, but unless your enlarger is short it is rarely necessary.
I see. Interesting on image quality on 8x10 contacts are nearly the same despite the lens' age. That's great to know as I figure one of these days, I'll go the Brian route and get a cheap but funtional view camera and one of these lenses to go along my Nikon 300M.
Also, that newsgroup articles a good read, Thanks Robert.
"Image quality" comprises a lot of things other than resolution and such. I would imagine that modern lenses will give you better contrast and will be sharper wide open than some of the lenses I like, even on an 8x10" contact print, but some of the older lenses are capable of smoother tonal gradation and rendering of out of focus areas than some of the more modern lenses, which may be overcorrected for my taste.
In response to Aggie's question--you should get good results with most lenses made by the major manufacturers since the era of multicoating (1970s), and even with many single coated lenses of modern design. If you're using relatively contemporary lenses for 4x5", you could set aside concerns about resolution and make your choices more on the basis of other factors that are usually at odds with each other: coverage, maximum aperture, weight and bulk, and cost.
Aggie, FWIW, For an enlarger lens, I split the difference between 105mm and 150mm and got myself a 135mm. Chrisl: As far as using vintage glass on the 8x10 goes, I have a problem using lenses that cost more than my car. see?
</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (MikeK @ May 14 2003, 06:07 PM)</td></tr><tr><td id='QUOTE'> My 8x10 is a restored Seneca City View ....I have acquired a 12" Kodak Commercial Ektar; </td></tr></table><span class='postcolor'>
I pretty much did the same thing, with a Seneca Improved and a 12 inch (300mm) Commercial Ektar in a shutter. It is a nice combination, and pretty light to carry too. I've been feeding it with Ilford 125 speed film. Camera $100 plus new ground glass. Lens and shutter $300.
Well, I got a lens today in shutter on Ebay. Thanks for the tip David http://apug.org/forum/html/emoticons/wink.gif I got a Turner-Reich convertible with a recently serviced shutter. The Camera is enroute. WooHoo! Ordered my Arista 400 film from Freestyle, now all I need to do is make a lensboard and get the lens mounted.